1. Field of the Invention
The present invention relates to an endoscope insertion assisting device for assisting insertion of an endoscope into a body cavity.
2. Description of the Related Art
An endoscope consists of an insertion section to be inserted into a body cavity, and an operating section for operating the insertion section. In an endoscopy, in particular, in a colorectal examination, since the large intestine has a winding structure in the body cavity, and is flexible and is fixed at only a few positions in the body cavity, the insertion operation of the endoscope is very difficult. Therefore, a lot of experience is required to acquire skills for inserting the endoscope into the large intestine. When the insertion skills are not sufficient, a test subject may suffer from great pain.
It is said that the most difficult part in the large intestine for insertion of the endoscope is so-called sigmoid colon and transverse colon, because of the following reasons. Unlike the other parts, the sigmoid colon and transverse colon are not fixed inside the body cavity, and therefore they may arbitrarily change in shape within a range of their own lengths, or may change in shape inside the body cavity due to contact force upon insertion of the endoscope. In view of the above, a lot of skills for making the sigmoid colon and transverse colon straight have been proposed, so as to reduce the contact between the endoscope and bowels at the time of inserting the endoscope as much as possible.
Further, there has been proposed a device for enabling an endoscope to be self-propelled in an insertion direction inside the bowels, so as to make it easy to insert the endoscope, even if the insertion skills are not sufficient. For example, Japanese Patent Translation Publication No. 2009-513250 discloses an endoscope insertion assisting device, in which a rotary body in the form of toroid (hollow cylinder) is rotated so as to cause friction force between an outer surface of the rotary body and bowel walls, and due to the friction force, propulsive force in an insertion direction is obtained.
In the insertion assisting device according to the above patent document, a cylindrical supporting member provided in a space inside the rotary body supports the rotary body in a rotatable manner, and the rotary body is sandwiched between driving gears disposed so as to come in contact with the outer surface of the rotary body rotating inside the supporting member and driven rollers disposed so as to be opposed to the driving gears across the rotary body, such that the rotary body rotates.
When the rotary body of the insertion assisting device configured as described above is thick and does not have sufficient flexibility, resist becomes larger at a front turned edge, a rear turned edge, and a driving section, and thereby the rotary body cannot rotate smoothly. In contrast, when the rotary body is thin and does not have sufficient strength, the driving force from the driving gears may not be adequately transmitted to the rotary body, or the rotary body may be broken due to friction at the driving section.
In view of the above, the thickness of a portion of the rotary body of the insertion assisting device, which is made in contact with the driving section, is made larger than those of other portions of the rotary body, such that a balance between the strength necessary for the driving and flexibility necessary for the smooth rotation is kept. In this case, each of the portions made thicker has a belt-like shape formed along a rotational direction of the rotary body. Accordingly, there are thick portions and thin portions along the circumferential direction of the rotary body. For example, according to the above patent document, the driving is performed in three portions, and therefore the thick portions are arranged at intervals of approximately 120 degrees in the circumferential direction of the rotary body.
However, in the case where there are the thick portions and the thin portions along the circumferential direction of the rotary body as described above, when the front end of the supporting member comes in contact with the inner wall surface of the body cavity, the thick portions of the rotary body come in point contact with the front end of the supporting member. Since the pressure is focused on the spot at which the point contact occurs, the rotary body is more likely to stop rotating by being influenced by the contact pressure in comparison with a rotary body having a uniform thickness.
When the rotary body stops rotating by being influenced by the contact pressure during the driving of the driving gears, holes may be made in the rotary body by idle rotation of the driving gears. Additionally, when a certain portion of the rotary body stops rotating, other portions of the rotary body may be forcibly advanced and drawn-in between the driving gears and the driven rollers to get stuck therebetween. In this case, even after the contact pressure is decreased, the rotary body cannot not rotate.